Fusible switch comprising a circuit breaker and current limiting fuse



Feb. 9, 1960 w, EDMUNDS I 2,924,686

FUSIBLE SWITCH COMPRISING A CIRCUIT BREAKER AND CURRENT LIMITING FUSEFiled Dec. 23, 1955 I 5 Sheets-Sheet 1 IN VEN TOR. Ill/UM #11010 [an/rmFeb. 9, 1960 w. H. EDMUNDS FUSIBLE SWITCH COMPRISING A CIRCUIT BREAKERAND CURRENT LIMITING FUSE 3 Sheets-Sheet 2 Filed D60. 23, 1955 Arracwzfs3 Sheets-Sheet 3 Feb. 9, 1960 w. H. EDMUNDS FUSIBLE SWITCH COMPRISING ACIRCUIT BREAKER AND CURRENT LIMITING FUSE Filed Dec. 25, 1955 INVENTOR.M/u/n/v/meaza EDMI/Nw 9% Arrap/m' s United States Patent FUSIBLE SWITCHCOMPRISING A CIRCUIT BREAKER AND CURRENT LIMITING FUSE William HaroldEdmunds, Havertown, Pa., assignor to I-T-E Circuit Breaker Company,Philadelphia, Pa., a corporation of Pennsylvania Application December23, 1955, Serial No. 555,073

4 Claims. (Cl. 200-114) My invention relates to fusible switches andmore particularly to a fusible switch comprising the series connectionof a circuit breaker and a current limiting fuse.

In my copending application Serial No. 461,378 filed October 11, 1954, Idescribe .a circuit breaker having overload features connected in serieswith a current limiting device, these two devices being electrically andmechanically coordinated.

In the instant invention I provide the same type of connection asindicated above but the circuit breaker is not provided with theoverload features and merely operates to interrupt normal load curent.That is to say, the circuit breaker will merely operate as a switch. Inseries with this circuit breaker or switch I provide a current limitingfuse of the type described in the above mentioned application Serial No.461,378 whereby op eration of the current limiting fuse energizes astriker pin which can be effective to operate the tripper bar of thecircuit breaker which in turn operates the circuit breaker contacts to adisengaged position.

Therefore, upon the occurence of a fault in one phase of a multiplephase system, the current limiting fuse of the faulted phase willoperate and, in view of the mechanical coordination between circuitbreaker and the fuse, the tripper bar of the circuit breaker will beoperated to cause contact disengagement for each phase of the system.

It is therefore apparent, that the application of my novel inventionwill prevent the serious condition of single phasing upon the occurenceof a single phase fault in the system being protected.

Another advantage which is inherent in my novel invent is that variousdesirable features such as under voltage devices, shunt trip and otherfeatures which are presently available for circuit breakers could beprovided. Similarly, remote tripping or remote closing of the device ispossible. Furthermore, the interrupting capacity of a circuit breaker isavailable for interrupting higher loads than a corresponding switchwould be able to interrupt.

Clearly the above features could not be obtained in presently usedfusible switches since a common tripper bar is not provided as in thecase of the circuit breaker of my novel invention, nor are the presentlyused switches provided with the arc extinguishing properties of thecircuit breaker.

It is now apparent that in view of the absence of overload sensingdevices for the circuit breaker, that this combination is moreeconomical than the circuit breaker and current limiting fusecombination described in my above mentioned copending application SerialNo. 461,378. Furthermore, all the advantages of the circuit breaker andcurrent limiting fuse combination are provided with the exception ofoverload devices for the circuit breaker. However, short circuitprotection is afforded by the current limiting fuse whereas in the case2,924,686 Patented Feb. 9, 1960 fusible switch utilizing a circuitbreaker as one com-' ponent whereby devices such as under voltagedevices, shunt trip and all other available devices for circuit breakersmay be applied to the combination.

My novel combination may be so constructed that the current limitingfuses may be assembled into a common housing and the circuit breaker isassembled into a second housing, these two assemblies being connectibleby means of disconnect contacts. I then so position the circuit breakertripper bar that it will be biased to disengage the circuit breakercontacts when the fuse assembly is not in place.

It is therefore seen that when the fuses are disconnected from thecircuit breaker that the circuit breaker contacts, if not in thedisengaged position, will be automatically disengaged.

In the case of presently used fusible switches this safety feature isnot provided and it is possible to remove one or more fuses while theswitch is closed, thereby leading to possible danger to the operatingpersonnel.

Another principal advantage of this type'of construction for a fusibleswitch is that by removing the current limiting fuse housing the load ispositively disconnected from the source, thereby adding anotherimportant safety feature to the fusible switch of my invention.

Accordingly, another object of my invention is to provide means wherebydisconnecting the fuse will automatically trip the circuit breaker.

A still further object of my invention is to provide a fusible switchutilizing a series connected circuit breaker and current limiting fusewhereby the load will be positively disconnected from the source whenthe current limiting fuse housing is being moved.

Another object of my invention is to provide a fusible switch whereincurrent limiting fuses are contained in a first assembly, a circuitbreaker is contained in a second assembly, and the two assemblies areelectrically connected and mechanically coordinated wherebydisconnecting of the two assemblies automatically disconnects thecircuit breaker contacts.

These and other objects of my invention will become apparent from thefollowing description taken in conjunction with the drawings in which:

Figure 1 shows a perspective view of a series connected circuit breakerand current limiting fuse constructed in accordance with my novelinvention.

Figure 2 is a cross-sectional side view of the fusible switch of Figure1.

Figure 3 is a cross-sectional view of a current limiting -fuse whichcould be utilized as the fuse element of my novel fusible switch.

Figure 4 is an exploded perspective view of a second embodiment of myinvention where the circuit breaker and the current limiting fuses whichform my novel invention are in separate housings.

Figure 5 is a cross-sectional side view through the fuse housing and aportion of the circuit breaker .of

Figure 4, and specifically shows the connection between is well known inthe art.

a current limiting fuse and the tripper bar of the circuit breaker.

Figure 6 is an electrical schematic diagram of the fusible switch of myinvention.

Figures 1 and 2 show a fusible switch comprising a circuit breakerwhichis mechanically coordinated with a current limiting device. Theoperating mechanism of the circuit breaker per se may be of any typewhich By wayof example, I have illust'rateda molded case circuit breakerof the type shown in United States Patent 2,574,093 issued Novemher 6,1951. The current limiting device which is used in coordination with thecircuit breaker may be of the type-shown in United States Patent2,592,399 issued April 8, 1952, and operates on the principles describedtherein.

As will be more fully explained hereinafter, coordination between 'thetwo devices is provided by the striker pin of the fuse and the tripperbar of the circuit breaker.

Referring now to Figures 1 and 2, the circuit breaker and the currentlimiting device are contained within the molded case housing 10, whichhas a cover 11 as seen in Figure 2. The circuit breaker is provided witha pair of cooperating contacts 12 and 13 for each pole, only one polebeing observable in Figure 2. Stationary con tact 12 is shown as beingconnected to the terminal 15 and the movable contact 13 is connected tothe movable contact arm 14. An arc chute 15a as seen in Figure 1 isprovided for each pole to aid in extinguishing the are created by thecooperating contacts 12 and 13 when these contacts are moved to thedisengaged position.

It should however be realized that since the interrupting duty of thecircuit breaker in my novel fusible switch will not be subjected toheavy interrupting duty that it maynot be necessary thatarcextinguishing means be provided.

The circuit breaker of Figures 1 and 2 then has a common tripper bar 16on which prop latch17 is mounted. As more clearly seen in Figure 2, theprop latch 17 engages the latch surface 18 of the member 19 which iscontrolled by the operating mechanism 20 of the circuit breaker. Whenthe latch surface 18 is positioned under the latch 17 and thehandle 21moved to the extreme right as illustrated in Figure 2 the cooperatingcontacts 12 and 13 are moved to their-engaged position.

However, if the'tripper bar 16 is rotated in a counterclockwisedirection, theprop latch 17 will be released the occurrence of a severeshort circuit current, the

current limiting device 25 will rupture thereby releasing its strikerpin 30 as will be more fully described, so that the strikernpin will bedriven forwardto engage the protrusion 23. This willrotate the commontripper bar 16in a'counterclockwisedirection to release the latch 17 and18 so that the cooperating contacts 12, 13 will be driven to theirdisengaged .position. "Obviously, the same operation would occurxifxthe.fuse of any other phase operates since it would engage-its correspondingtripper bar protrusion.

Current limiting device 25 may be positioned within the circuit breakerin any desirable manner, as for example by clips which are not shown inthefigure but would be constructed to connect the terminals 32 and 33 toterminals 34 and 35of the current limiting de- -vice"25.'

Thustheele'ctrical circuit of'the one'phase'ofthe ingdevice '25 isprovided with a striker pin 30 which is biased to the right by means ofspring 39. However, the thin wire 40 prevents the spring 39 from drivingthe striker pin 30 forward. The circuit interrupter 25 is providedinternally with terminal blocks 41 which secure the inner units 42. Theinner units 42 are constructed in substantially the same manner as shown1n United States Patent 2,592,399 issued April 8, 1952, wherein areduced cross-sectional fusible element is surrounded by quartz crystalsso that the rupture of the fusible element will result in a melting ofthe quartz crystals permitting it to flow between the gap created by therupture to result in extremely rapid interruption of the arc.

This particular device will operate within less than one-fourth of acycle so that the let-through current is less than 10% of the availableshort-circuitcurrent and still not more than thirty times the magnitudeof the rated current.

As further seen in Figure 3, the inner unit 42' which contains the mainportion of the current limiting device is connected in electricalparallel with the thin wire 40. A quartz filler 44 surrounds both theinner unit 42 and the thin wire 40. Following the rupture of the innerunit 42, all of the current will be diverted to the thin wire 40. Due tothe small cross-sectional area of the wire 40, it will rupturesubstantially instantaneously thereby enabling the spring 39 to releaseits energy to drive the striker pin30 forward.

It is now possible to consider the operation of my novel fusible switchas shown in Figures 1, 2 and 3. It is understood that in the case of afault in one of the phases that the wire 40 will be broken. The breakingof the wire 40 will release the stored energy in the biasing spring 39to thereby drive the striker pin 30 upward to engage the respectiveprotrusion 23 of the common tripper bar 16 to effect release of thelatch 17-18 so that the cooperating contacts 12-13 of each phase will bemoved to their disengaged position.

That is, even though-a severe short-circuit may exist ononly one pole ofa multi-phase line, the current limiting device associated with thatpole will'operate. However, after the fuse operation, the mechanicalcoordination between thisunit and the circuit breaker will result in theopening of all three. poles of a circuit breakernin it is inherentin'the device that the load is positively disconnected from the sourceby means of the disengaged circuit breaker contacts when fuses are beingreplaced. It is further understood that the circuit breaker of Figures1, 2 and 3 could have been provided with various circuit breakerauxiliary equipment such as under-voltage devices, shunt trip, and soon. Similarly, remote tripping or remote closing. could havebeenprovided.

A second possible form which my novel invention can take is shown inFigures 4 and 5. As shown specifically in the exploded perspective viewof Figure 4, the current limiting devices can be assembled in anindividual unit shown generally at 50 for cooperation with a circuitbreaker 51 which could have the same type of operating mechanism as thecircuit breaker shown in Figures 1 and 2.

The fuse housing '50 rand the circuit breaker 51 tare provided withdisconnect contacts of the type described in copending applicationSerial No. 536,586 filed September 26, 1955 whereby each pair ofdisconnect contacts 52-53, 54-55 and 5657 cooperate with the circuitbreaker contacts 58-59, 6061 and 62-63 respectively.

As shown in Figure 5, which is a section taken through one phase of thedevice of Figure 4, the contacts 52 and 53 of the fuse housing 50connect the current limiting fuse 25 which may be of the type shown inFigure 3 in series with a corresponding circuit breaker phase which hasthe disconnect contacts 5859.

The tripper bar 16 of Figure 5 is shown as having a link 64 which isbiased to move to the left by the biasing means 65 thereby maintainingthe left hand tip 66 of the link 64 as seen in each of Figures 4 and 5in engagement with a protrusion 67 of the link 68. Link 68 which ispivotally mounted at pivot point 69 of the fuse housing 50 and the upperportion 70 of the link 67 are biased in a counterclockwise directionabout the pivot point 69 by means of the biasing spring 71 to overcomethe effect of biasing spring 65 when the fuse assembly is connected tothe normal operating position as shown in the solid lines of Figure 5.The extension 72 of the tripper bar 16 prevents counterclockwiserotation of the tripper bar 16 by engaging the notch 73 of the link 64.Upon the occurrence of a fault however, the striker pin 74 of thecurrent limiting fuse 25 will protrude through the aperture 75 to engagethe portion 70 of the pivotally mounted link 67 in such a manner as toovercome the force of biasing spring 71 and allow the link 64 to movetoward the left by the force of the biasing spring 65. This position isshown in the dotted line view of Figure 5. Clearly, the tripper bar 16will rotate in a counterclockwise direction and the prop latch will asis shown in conjunction with Figures 1, 2 and 3 allow contactdisengagement of the circuit breaker contacts. It is to be noted inconjunction with Figures 4 and 5, that each of the fusible elements 25corresponding to each phase of the system can operate the tripper bar 16to cause contact disengagement of circuit breaker contact. Hence, it isseen that in the case of the device of Figures 4 and 5 that singlephasing is prevented since a fault when any of the phases will causeoperation of the circuit breaker contact to their disengaged position.

Hence, the fusible switch shown in Figures 4 and 5 operates in the samemanner as does the fusible switch shown in Figures 1 and 2. However, thedistinction here is that the components comprising the circuit breakerand the fusible switch are mounted in separate and interchangeableassemblies thereby providing extreme flexibility for installation andmaintenance of the system.

Another important advantage provided by the fusible switch of Figures 4and 5 is that upon disconnection of the fuse assembly 50 and the circuitbreaker 51, that positive disconnection between the fuse terminals andthe line is effected to thereby allow safe maintenance of the fuses.

This may be more clearly undertsood with reference to Figure 6 whichshows a diagrammatic circuit of the device of Figures 4 and 5.

In Figure 6, the fuse terminals 52, 54 and 56 of Figure 4 are shown asbeing connected to the load terminals 80, 81 and 82 respectively. Thefuse terminals 53, 55 and 57 are then shown as being connected to thecircuit breaker terminals 59, 61 and 63 respectively as was the case ofFigure 4. The circuit breaker terminals 83, 84 and 85 are then connectedto the line terminals 86, 87 and 88 respectively.

Consider now that it is desired to replace a fuse or in some manner workon the fuse assembly 50.

If the fuse assembly is removed, it has been seen that the circuitbreaker contacts are automatically moved to the disengaged position andhousing 50 must be disconnected to achieve entrance to the individualfuse ele- 6 ments. It is to be noted that the circuit breaker will beopened even if maintenance personnel neglected to operate the circuitbreaker prior to attending to work on the housing 50.

While working on the disconnected housing 50 however, it is essential tonote that the fuse terminals are completely isolated from line terminals86, 87 and 88 by virtue of the disengaged circuit breaker contacts atterminals 59, 61 and 63. Hence, maintenance personnel are subjected tono shock hazard when working on the current limiting fuses.

In the foregoing we have described my invention solely in connectionwith specific illustrative embodiments thereof. Since many variationsand modifications of the invention will now be obvious to those skilledin the art, we prefer to be bound not by the specific disclosures hereincontained but only by the appended claims.

I claim:

1. A multiphase fusible switch; said multiphase fusible switchcomprising a multiphase circuit breaker and a current limiting fuse foreach phase of said multiphase circuit breaker; said circuit breakerbeing constructed to be non-responsive to electrical overloadconditions; said circuit breaker comprising a pair of cooperablecontacts for each phase, a common latch means to maintain each pair ofsaid cooperable contacts in an engaged position, means to move saidcooperable contacts to a disengaged position responsive to defeat ofsaid latch means and a tripper bar; said tripper bar being operativelyconnected to said latch means to defeat said latch means responsive tooperation of said tripper bar; said current limiting fuses beingassembled in a first housing; said circuit breaker being assembled in asecond housing; said first and second housings having disconnectcontacts arranged to connect one of said current limiting fuses inseries with a pair of circuit breaker cooperable contacts for each phaseof said multiphase circuit breaker; each of said current limiting fusesbeing operatively connected to said circuit breaker tripper bar wherebyelectrical disconnection between said current limiting fuse and saidcircuit breaker cooperable contacts operates said tripper bar todisengage said cooperable contacts; operation of the current limitingfuse of any phase thereby being operative to defeat said common latchmeans and disengage the cooperable contacts of each phase.

2. A multiphase fusible switch; said multiphase fusible switchcomprising a multiphase circuit breaker and a current limiting fuse foreach phase of said multiphase circuit breaker; said circuit breakerbeing constructed to be non-responsive to electrical overloadconditions; said circuit breaker comprising a pair of cooperablecontacts for each phase, a common latch means to maintain each pair ofsaid cooperable contacts in an engaged position, means to move saidcooperable contacts to a disengaged position responsive to defeat ofsaid latch means and a tripper bar; said tripper bar being operativelyconnected to said latch means to defeat said latch means responsive tooperation of said tripper bar; said current limiting fuses beingassembled in a first housing; said circuit breaker being assembled in asecond housing; said first and second housings having disconnectcontacts arranged to connect one of said current limiting fuses inseries with a pair of circuit breaker cooperable contacts for each phaseof said multiphase circuit breaker; each of said current limiting fusesbeing positioned to operate said circuit breaker tripper bar responsiveto operation of said current limiting fuses; said current limiting fusebeing operatively connected to said circuit breaker tripper bar wherebyelectrical disconnection between said current limiting fuse and saidcircuit breaker cooperable contacts operates said tripper bar todisengage said cooperable contacts.

3. A multiphase fusible switch; said multiphase fusible switchcomprising a multiphase circuit breaker and a current limiting fuse foreach phase of said multiphase 7 circuit breaker; said circuit breakerbeing constructed to be non-responsive to electrical overloadconditions; said circuit breakercompri'sing a pair of cooperablecontacts for each, phase, a common latch means to maintain each pair ofsaid cooperable contacts in an'engaged position, means to move saidcooperable contacts to a disengaged position responsive to defeat ofsaid latch means and a tripper bar; said tripper bar being operativelyconnected to said latch means to defeat said latch means responsive tooperation of said tripper bar; said current limiting fuses beingassembled in a firsthousing; said circuit breaker being assembled in asecond housing; said first and second housings having disconnectcontacts arranged to connect one of said current limiting fuses inserieswith a pair of circuit breaker cooperable contacts for each phase ofsaid multiphase circuit breaker; each of said current limiting fusesbeing operatively connected to said circuit breaker tripper bar wherebyelectrical disconnection between said current limiting fuse and saidcircuit breaker cooperable contacts operates said tripper bar todisengage said cooperable contacts; operation of the current limitingfuse of any phase thereby being operative to defeat said common latchmeans and. disengage the cooperable contacts'of each phase; said circuitbreaker terminals being connected to a power source, said currentlimiting fuse terminals being connected to a load; disconnection of saidfirst housing from said second housing providing positive disconnectionof said current limiting fuse terminals.

I 4. A multiphase fusible switch; said multiphase fusible switchcomprising a multiphase circuit breaker and a current limiting fuse foreach phase of said multiphase circuit breaker; said circuit breakerbeing constructed to be non-responsive to electrical overloadconditions; said circuit breaker comprising a pair of cooperablecontacts for each phase, a common latch means to maintain each pair ofsaid cooperable contacts in an engaged position, means to move saidcooperable contacts to a disengaged position responsive to defeat ofsaid latch means and a tripper bar; said tripper bar being operativelyconnected to said latch means to defeat said latch means responsive tooperation of said tripper bar; said current limiting fusestbeingassembled in a first housing; said circuit breaker being assembled in asecond housingysaid first and second housings having disconnect contactsarranged to connect one of said current limiting fuses in serieswith apair of circuit breaker'cooperable contacts for each phase of saidmultiphase circuit breaker; each of said current limiting fusesbeingpositioned to operate said circuit breaker tripper bar responsive tooperation of said current limiting fuses; said current limiting. fusebeing operatively connected to said circuit breaker tripper bar wherebyelectrical disconnection between said current limiting fuse and saidcircuit breaker'cooperable contacts operates said tripper bar todisengage .said cooperable contacts; said circuit breaker terminalsbeing connected to a power source said current limiting fuse terminalsbeing connected to, a load;.disconnection of said'first housing fromsaid second housing providing positive disconnection of said currentlimiting fuse terminals.

References Cited in the fileof this. patent UNITED STATES PATENTS

